There is no necessary to set these App settings to deploy laravel apps to Azure Web Apps via Git. And by default, the root directory of the web app on Azure is
D:\home\site\wwwroot\, usually we don’t need to change it.
You can refer to this answer of Deploy Laravel to Azure to get steps of deploying laravel app to Azure. Also if you need to expose public folder to public, you may refer to laravel 5.1 on windows azure web application.
Especially, according your error message, it seems that you leverage several symfony packages, here is a similar thread on SO "Unable to kill the process" error with "php composer.phar install" on Azure, you can try the methods mentioned there. Otherwise, you can try to first delete cache files, then run the composer command.